“The first 90% of the code accounts for the first 90% of the
development time. The remaining 10% of the code accounts for the other 90%
of the development time.” Attributed to Tom Cargill of Bell Labs,
and popularized by Jon Bentley's September 1985 Bumper-Sticker
Computer Science column in Communications of the
ACM. It was there called the “Rule of
Credibility”, a name which seems not to have stuck. Other maxims in
the same vein include the law attributed to the early British computer
scientist Douglas Hartree: “The time from now until the completion of
the project tends to become constant.”